1. Dakumar
machiner
y Co.,Ltd www.dakumar.com
How to choose plastic injection molding machine
Typically, the important factors when choosing plastic injection molding
machine include mold, product, molding requirements and so on. Therefore,
you must collect or have the following information before making a choice:
mold dimension (width, height, thickness), weight and special design; types
and amount of the plastic (single or multiple plastic materials); dimensions
and weight of injection molding product (length, width, height, thickness);
molding requirements, such as quality condition, production speed and so on.
In obtaining the above information, you can follow these steps to choose a
suitable plastic injection molding machine:
Choose the right type of plastic injection molding machine: make decision
by the products and plastic
The plastic injection molding machine has a lot of types, so at the
beginning, you should determine that what kind or which series of plastic
injection molding machine is fit
for the product. For example, for
thermoplastic plastic or Bakelite
resin or PET, the product is single
color, two-color, multi-color,
laminated or blending. In addition,
some product requires high
stability (closed loop), high
precision, high injection speed,
high injection pressure and rapid production (multi-loop) and so on.
Able to put it on: the size of mold determine whether the internal spur
of large column, the mold thickness, the minimum mold dimension and
the mold plate size of plastic injection molding machine are suitable or not,
to make sure that it is able to put mold on.
The mold width and height must be less than or at least less than the
internal spur of large column; The mold width and height must in the
mold plate size range; the mold thickness should be between the
thickness of plastic injection molding machine; The mold width and height
must be fit with the minimum mold size recommended by the plastic
injection molding machine.
Able to put it out: the mold and product judge whether the “Opening
Stroke” and “Ejector Stroke” are enough to remove the finished product.
The opening stroke should at least larger than the product height along
the opening direction more than twice, including the length of vertical
sprue; ejector stroke should long enough to eject the finished product.
Able to maintain locked: the product and plastic determine the tonnage of
“clamping force”.
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2. Dakumar
machiner
y Co.,Ltd www.dakumar.com
When the raw materials inject into the mold cavity in a high pressure, it
will create a bulging force, so the clamping unit of the plastic injection
molding machine should provide sufficient “clamping force” so that the
mold was not subject to distraction. The need of clamping force is
calculated as follows:
Clamping force = projected area of
product in the direction of opening and
closing mould (cm2) ×the number of
mold cavity×in-mold pressure
(kg/cm2);
Projected area of product in the
direction of opening and closing mould
is generated by the product appearance size.
In-mold pressure is different with different materials, generally take 350-
400 kg/cm2.
The machine clamping force is usually greater than 1.17 times of the
bulging force.
Enough injection quantity: the weight of product and the number of mold
cavity determine the “injection quantity” and select the appropriate
“screw diameter”.
For stability purpose, the injection volume required for more than 1.35
times of the product, which means the product weight should less than 75%
of the injection amount.
Good injection: plastic determine “screw compression ratio” and
“injection pressure” and other conditions.
Some plastic requires a higher injection pressure and appropriate screw
compression ratio for a good molding. So when choosing screw, it should
considered about the demand of injection pressure and the problems of
compression ratio. In general, smaller diameter screw provides higher
injection pressure.
High injection speed: confirm the injection speed.
Some product requires a high injection speed to stabilize the injection
molding, such as ultra-thin wall product. In this case, it is necessary to
make sure that whether the injection speed and injection rate are enough
or not, and whether accumulator and closed-loop control are necessary or
not. Generally speaking, in the same condition, a screw in the plastic
injection molding machine with high injection pressure has a lower
injection speed, on the contrary, a screw with low injection pressure has a
higher injection speed. So when choosing the screw diameter, injection
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3. Dakumar
machiner
y Co.,Ltd www.dakumar.com
volume, injection pressure, and injection rate (injection speed) should be
cross considered.
Dakumar is one of the Chinese leading innovators for plastic molding
machine's researching and developing. It provides various plastic injection
molding machines and plastic molding auxiliary machines, you can get
what you want in Dakumar machinery Co.,Ltd.
(edit by DAKUMAR)
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